Unlike spoken languages, sign languages of the deaf make use of two
primary articulators, the right and left hands, to produce signs, This
situation has no obvious parallel in spoken languages, in which speech
articulation is carried out by symmetrical unitary midline vocal
structures. This arrangement affords a unique opportunity to examine the
robustness of linguistic systems that underlie language production in
the face of contrasting articulatory demands and to chart the
differential effects of handedness for highly skilled movements.
Positron emission tomography (PET) technique was used to examine brain
activation in 16 deaf users of American Sign Language (ASL) while
subjects generated verb signs independently with their right dominant
and left nondominant hands (compared to the repetition of noun signs),
Nearly identical patterns of left inferior frontal and right cerebellum
activity were observed. This pattern of activation during signing is
consistent with patterns that have been reported for spoken languages
including evidence for specializations of inferior frontal regions
related to lexical- semantic processing, search and retrieval, and
phonological encoding. These results indicate that lexical-semantic
processing in production relies upon left-hemisphere regions regardless
of the modality in which a language is realized, and that this left-
hemisphere activation is stable, even in the face of conflicting
articulatory demands. in addition, these data provide evidence for the
role of the right posterolateral cerebellum in linguistic-cognitive
processing and evidence of a left ventral fusiform contribution to sign
language processing.

A large number of imaging studies have identified a role for the
posterior parietal lobe, in particular Brodmann's area 7 and the
intraparietal sulcus (IPS), in mental rotation. Here we investigated
whether neural activity in the posterior parietal lobe is essential for
successful mental rotation performance by observing the effects of
interrupting this activity during the execution of a mental rotation
task. Repetitive transcranial magnetic stimulation (rTMS) was applied to
posterior parietal locations estimated to overlie Brodmann's area 7 in
the right and the left hemisphere, or to a posterior midline location
(sham condition). In three separate experiments, rTMS (four pulses, 20
Hz) was delivered at these locations either 200-400, 400-600, or 600-800
msec after the onset of a mental rotation trial. Disrupting neural
activity in the right parietal lobe interfered with task performance,
but only when rTMS was delivered 400 to 600 msec after stimulus onset.
Stimulation of the left parietal lobe did not reliably affect mental
rotation performance at any of the time points investigated. The time-
limited effect of rTMS was replicated in a fourth experiment that
directly compared the effects of rTMS applied to the right parietal lobe
either 200-400 or 400-600 msec into the mental rotation trial. The
results indicate that the right superior posterior parietal lobe plays
an essential role in mental rotation, consistent with its involvement in
a variety of visuospatial and visuomotor transformations.

We used functional imaging of normal subjects to identify the neural
substrate for the perception of voices in external auditory space. This
fundamental process can be abnormal in psychosis, when voices that are
not true external auditory objects (auditory verbal hallucinations) may
appear to originate in external space. The perception of voices as
objects in external space depends on filtering by the outer ear.
Psychoses that distort this process involve the cerebral cortex.
Functional magnetic resonance imaging was carried out on 12 normal
subjects using an inside-the-scanner simulation of 'inside head' and
'outside head' voices in the form of typical auditory verbal
hallucinations. Comparison between the brain activity associated with
the two conditions allowed us to test the hypothesis that the perception
of voices in external space ('outside head') is subserved by a
temperoparietal network comprising association auditory cortex posterior
to Heschl's gyrus [planum temporale (PT)] and inferior parietal lobule.
Group analyses of response to 'outside head' versus 'inside head' voices
showed significant activation solely in the left PT. This was
demonstrated in three experiments in which the predominant
lateralization of the stimulus was to the right, to the left or
balanced. These findings suggest a critical involvement of the left PT
in the perception of voices in external space that is not dependent on
precise spatial location. Based on this, we suggest a model for the
false perception of externally located auditory verbal hallucinations.

Early onset blindness provides a lesion model to investigate whether
experience-dependent mechanisms subtend the functional anatomy of
semantic retrieval. In particular, visual deprivation might alter the
neural systems underlying retrieval of semantic information that is
acquired via visual experience. Using functional MRI, we demonstrate
that both early blind and sighted subjects activate a left-lateralized
fronto-temporal 'core' semantic retrieval system and show common effects
for retrieval of visually experienced semantic information. However,
irrespective of the type of semantics, blind subjects activate
additional extrastriate regions, which are coupled with frontal and
temporal semantic regions. The resilience of semantic retrieval
responses to visual deprivation suggests a considerable degree of innate
and epigenetic specification of the semantic system. In contrast, the
exuberant functional connectivity between extrastriate and 'core'
semantic retrieval regions might be explained by abnormal pruning
processes during early neurodevelopment.

Autobiographical memory relies on complex interactions between episodic
memory contents, associated emotions and a sense of self-continuity
along the time axis of one's life history. The neural correlates
underlying autobiographical memory are known to primarily comprise areas
of prefrontal cortex, medial and lateral temporal cortex, as well as
posterior cingulate and retrosplenial cortex. By contrast, the effect of
encoding and/or storage parameters such as the emotional tone of the
memories retrieved or the length of the time-interval between the
initial encoding of information and retrieval remains to be clarified.
…we investigated the impact of remoteness and emotional valence on the
neural correlates of autobiographical memory retrieval. Changes in
neural activity related to autobiographical memory retrieval
(irrespective of remoteness and emotional tone) relative to baseline
were observed bilaterally in medial and lateral temporal, temporal-
occipital, posterior cingulate and frontal cortices. Recent (relative to
remote) memories were associated with differentially increased neural
activity bilaterally in the retrosplenial cortex and the hippocampal
region, whereas remote (relative to recent) memories did not show any
statistically significant differential neural activations. Positive
(relative to negative) memories bilaterally activated the orbitofrontal
cortex, the temporal pole, as well as medial temporal areas, with the
activation peak being in the entorhinal region. By contrast, negative
(relative to positive) memories differentially increased neural activity
in the right middle temporal gyrus only. The data suggest differential
functional roles for temporal, prefrontal and retrosplenial regions
during autobiographical memory retrieval depending on the remoteness and
the emotional valence of the memories retrieved. In particular, our
findings support the 'classic' model of long-term memory processing,
which suggests a time-limited differential involvement of the
hippocampus in memory consolidation. Interestingly, the observation of
such a time-dependent involvement of the hippocampal region in memory
consolidation corresponds to the course of retrograde amnesia observed
in demented patients, with the loss of recent memories appearing during
early stages of the disease.. Only during later stages do remote
memories also become impaired. We conclude that the brain regions
involved in autobiographical memory retrieval are influenced by the
triggered memories' emotional significance and their relationship to the
individual time axis.

A unique feature of Japanese language is that its written sentences
consist of both morphograms (kanji) and syllabograms (kana). Despite
extensive research by PET, functional MRI and MEG, the issues of the
difference (or the similarities) between the processing of kanji and
kana, and between word reading and object/picture naming have not been
resolved as yet. This study investigated the function of the posterior
basal temporal area in the language dominant hemisphere in auditory and
visual language processing, with special emphasis on semantic and
phonological recognition. Subdural electrode grids were placed on the
left temporal area of a right-handed woman with intractable temporal
lobe epilepsy as part of a pre-surgical evaluation. Her dominant
hemisphere for language was shown to be the left on the Wada test.
Electric stimulation of 50 Hz was applied to the electrodes during the
tasks related to language. Our results showed a clear distinction in the
responses and/or performance of the subject depending on the type of
characters presented and the tasks employed. Electric stimulation of a
localized area in the posterior basal temporal lobe caused neither
comprehensive nor productive deficit in the tasks using auditory
stimuli. In the tasks using visual stimuli, in contrast, impairments
were observed in (i) reading of kanji words and (ii) naming of
objects/pictures and geometric designs, but not in (iii) reading of
kana, (iv) copying of kanji, kana and geometric designs, and (v) using
tools. The subject maintained full comprehension of spoken language,
suggesting that the auditory tasks are not processed in the posterior
basal temporal area. The fact that the impairment of kanji reading and
disturbance of object/picture naming were elicited by electric
stimulation of the same area indicates that there is at least one
anatomical area that is used commonly for kanji (but not kana) and
object processing. The conceptual entity of the test items supposedly
was recognized correctly, but the concept failed to be matched to
correct phonological representation. The left posterior basal temporal
area, therefore, has an important function of connecting visual semantic
information into phonological representation.